Novel Screen-Printed Sensor with Chemically Deposited Boron-Doped Diamond Electrode: Preparation, Characterization, and Application.

New screen-printed sensor with a boron-doped diamond working electrode (SP/BDDE) was fabricated using a large-area linear antenna microwave chemical deposition vapor system (LA-MWCVD) with a novel precursor composition. It combines the advantages of disposable printed sensors, such as tailored design, low cost, and easy mass production, with excellent electrochemical properties of BDDE, including a wide available potential window, low background currents, chemical resistance, and resistance to passivation. The newly prepared SP/BDDEs were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry and electrochemical impedance spectroscopy using inner sphere ([Fe(CN)6]4-/3-) and outer sphere ([Ru(NH3)6]2+/3+) redox probes. Moreover, the applicability of these new sensors was verified by analysis of the anti-inflammatory drug lornoxicam in model and pharmaceutical samples. Using optimized differential pulse voltammetry in Britton-Robinson buffer of pH 3, detection limits for lornoxicam were 9 × 10-8 mol L-1. The oxidation mechanism of lornoxicam was investigated using bulk electrolysis and online electrochemical cell with mass spectrometry; nine distinct reaction steps and corresponding products and intermediates were identified.

Doping Level of Boron-Doped Diamond Electrodes Controls the Grafting Density of Functional Groups for DNA Assays.

The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20,000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays.